جستجوی مقالات مرتبط با کلیدواژه « Growth parameters » در نشریات گروه « شیلات »

The European pilchard (Sardina pilchardus) plays a crucial role along the Algerian coast, forming a significant part of the local fisheries industry. However, overfishing has resulted in a decline in their population, which has had adverse effects on the fishery sector. This study was conducted to evaluate the current mortality rate and exploitation rate of the sardine S. pilchardus and investigate its growth and length-weight relationship along the Ghazaouet coast. A sample of 1576 specimens was collected from commercial purse seine catches on the western Algerian coast (Ghazaouet fishing grounds). The total length (TL) of the specimens ranged from 9.6 to 21.4 cm with an average of 14.6±1.86 cm, and the total weight (TW) varied between 6.2 and 57.8 g with an average of 25.4±9.57 g. The estimated growth parameters using the Von Bertalanffy approach have an asymptotic length L∞=21.26 cm, growth coefficient K=0.77 year-1, and age at zero length t0=-0.17 year. The results of the study showed that the length-weight relationship had an isometric growth (b=2.99) with a high correlation (r=0.95). The sex ratio showed no dominance between males and females (F+M/M=0.5). The instantaneous rate of total mortality (Z) was estimated to be 1.79 per year, with natural mortality (M) estimated at 0.65 year-1. Fishing mortality (F) and exploitation (E) were estimated at 1.14 and 0.64 year-1, respectively. Based on these results, the sardine stock in the southwestern Mediterranean Sea (western Algerian coast) is under higher fishing pressure. Consequently, it is imperative to implement management strategies that ensure sustainable levels of harvesting.

Population dynamics of skinnycheek lanternfish, Benthosema pterotum (Alcock, 1890), were studied in the Oman Sea from January to December 2019. A total of 2893 individuals were sampled from the commercial catch of bottom trawlers in the Oman Sea. The total length (TL) ranged from 21-60 mm and the average length was 39.4±4.64 mm. More than 84% of the samples were between 33-45 mm TL. The length-weight relationship was obtained TW=0.00008 TL 2.38 and showed negative allometric growth. The asymptotic length (Loo) and growth coefficient (K) were estimated at 63 mm and 1.6 per year, respectively. In addition, tmax and t0 were calculated at 1.73 and -0.15 year,   respectively. The von Bertalanffy growth equation was calculated as Lt=63 (1 – e -1.6(t+0.15)). The coefficients of total mortality (Z), instantaneous natural mortality (M), and fishing mortality (F) rates were estimated as 6.65 per year, 2.62 per year, and 4.03 per year, respectively. Size at first capture (Lc) was estimated at 35.67 mm (TL). The current rate of exploitation (E) was given as 0.6 and therefore, the values of exploitation ratio were reasonable for the current fishing effort.

Goatfishes (Teleostei, Mullidae) are a group of mainly coastal fishes that form an important part of food chains, and also have commercial value. In addition, they are valuable fishes in ecosystem monitoring and management programs because they are sensitive to human-induced activities such as fisheries and habitat modification. Mathematical models of fish growth provide an objective and practical method for description of growth parameters and estimation of fish weight at different time series. This study presents and describes length-weight relationships for nine goatfish species belonging to three genera (Mulloidichthys, Parupeneus and Upeneus) collected from the Persian Gulf and Oman Sea. The estimated parameter "˜b' values ranged from The slope (b) of LWRs for all mullid species fell within the expected range of 2-4 varying from 2.370 for Parupeneus heptacanthus to 3.179 for Upeneus vittatus based on TL and from 2.391 for U. sundaicus to 3.804 for P. rubescens based on SL,

West African ladyfish, Elops lacerta is a pelagic fish present in the coastal waters of West Africa from Mauritania to Angola. This study is conducted to provide data on the growth and exploitation parameters of E. lacerta important for the management and conservation of this species in the Ivorian’s Exclusive Economic Zone (EEZ). These parameters were estimated by the indirect method using length frequency data collected in the Ivorian’s EEZ during January 2019 to December 2020. Monthly length frequency data were analyzed by FiSAT II software. A total of 865 specimens were examined. The growth parameters from von Bertalanffy growth function (VBGF) estimations were L∞ = 60.38 cm fork length, K = 0.39 year−1, and t0 = 0.46 year. The estimated potential longevity (tmax) was 7.69 years. The exploitation parameters showed that the total mortality rate (Z), natural mortality rate (M) at 28.35°C and fishing mortality rate (F) were 1.57 year−1, 0.80 year−1 and 0.77 year−1, respectively. The exploitation rate (E = F/Z) was 0.49. This value is lower than the optimal exploitation value (E50), thus expressing a case of under-exploitation of the species in the Ivorian’s EEZ. The size of first capture (Lc) below the size of first sexual maturity (FL50) and the optimal size of capture (Lopt) requires the implementation of an adequate mesh size management policy to allow fish to reproduce several times before being captured.

The main objective of this study was to examine the growth, mortality, and exploitation rate of Chloroscombrus chrysurus from the continental shelf of Ghana, West Africa between July 2018 and June 2019. This study provided results on fishery dynamics parameters to contribute to estimating the stock assessment of these fish species. Monthly length-frequency data were collected from 697 samples and analyzed using fisheries models fitted in TropFish R. The von Bertalanffy growth parameters were utilized to analyze the population dynamics of these species using ELEFAN Simulating Annealing. The estimated asymptotic total length (L∞), coefficient of growth (K), and growth performance index (Φ′) was 24.9 cm, 0.84 year-1, and 2.72, respectively, with a Response surface (Rn) value of 0.79. The total mortality (Z), natural mortality (M), and fishing mortality (F) rates C. chrysurus from the continental shelf of Ghana were 3.27 year-1, 1.31 year-1, and 1.96 year-1, respectively. The exploitation rate (E) estimated was above the optimum level of 0.5 which indicates that the species is overexploited. Based on the Emsy (0.69) value, analyses show that the exploitation rate has exceeded the sustainable limit and hence the need for proper fisheries management measures.

This study was conducted in two experiments. Experiment 1 aimed to investigate the growth promoting and anti-oxidative effects of Azolla nilotica (AZN) and Spirulina platensis (SP) in Oreochromis niloticus. Seven fish groups (G1-G7), each in three replicates, were fed a basal diet (control), AZN 5%, AZN 10%, SP 0.5%, SP 1%, a mixture of Azolla nilotica 5% and Spirulina platensis 1% (AZN 5 %-SP 1% mix), and a mixture of Azolla nilotica 10% and Spirulina platensis 1% (AZN 10% - SP 1% mix), respectively, for 3 months. The results showed a significant increase in growth indices (weight gain, specific growth rate, average length gain, feed efficiency ratio), and a decrease in the feed conversion ratio in all supplemented groups compared to control. Hepato-somatic index in G4 and G5 groups, and intestinal-somatic index in G4 - G6, and in G5 and G6 were obviously higher than control. Spleno-somatic index and antioxidant enzymes (GSH-px, SOD and CAT) markedly increased in G5 and G6 compared to control. Significant increase (p<0.05) in white blood cells was recorded in G2 and G4. Experiment 2 verified the effect of one-month supplementation of SP 1% on males and females O. niloticus fecundity. Males fed with SP 1% had an enhanced fertility as indicated by an increase in sperm density, spermatozoa motility and livability rates compared with the control. There was a significant increase in eggs number and the fecundity index in unripe females and a tendency of egg size to increase in ripen fish. It could be concluded that SP 1% and AZN 5% supplementation is advantageous to improve O. niloticus growth and fecundity.

In the last three decades, several ecological factors were changed and affected the most important commercial fish stocks in the Caspian Sea. This paper aims to assess the effects of these pressures on the population structure, stock status and the vulnerability risk of stock extinction of the stellate sturgeon (Acipenser stellatus Pallas, 1771) in the Southern Caspian Sea, in the years 1990-2011. For this period, we estimated growth parameters, the age structure of catch, sexual maturity, age at first capture, natural and fishing mortality, biomass and risk of stock extinction of stellate sturgeon by IUCN Red List categories. Fork lengths of individuals ranged from 82 to 206 cm and ages from 4 to 29 years. The growth parameters were L∞=215.0 cm, K= 0.064 year−1, t0=−3.2 years. The majority of the catch (67.4-90.1%, averaged 80.0%) belonged to 9-13 years old. The biomass had a descending trend from 4983.5 mt in 1990-91 declined to 10.6 mt in 2011-12. The generation length was 16 years. Stock status indicators showed that 89% of catch were mature individuals, mature and optimum fish length comprised 74% and 10% of the fish captured comprise mega-spawners. This study revealed that the stock of the stellate sturgeon is being overfished for the whole years and critically endangered.

The population structure of Aphanius mento in the Seyhan Reservoir was studied on the basis of 834 fish specimens (516 males and 318 females) caught on a monthly basisbetween September 2013 and August 2014. Fish were collected using dip nets of tulle with a 1mm mesh size. The maximum age of fish was found to be 4 years for both sexes combined, the 1 year old age group comprised 62.20% of male samples. The overall sex ratio of females to males was 1:1.62. Von Bertalanffy growth parameters were L∞=54.33 mm, K=0.399 year-1,  t0 =-1.168 years for females, L∞ =52.72 mm, K=0.397 year-1, t0=-1.137 years for males, and L∞=56.50 mm, K=0.386 year-1,                t0=-1.257 years for both sexes. The length (TL) - weight (W) relationship was W= 0.00051xTL2.635, (r= 0.965) for males, W=0.00088xTL2.464, (r= 0.987) for females and W=0.00066xTL2.554, (r = 0.974) for both sexes. Condition factor ranged from 1.696 for males and 1.613 for females to 1.664 for both sexes. The mean condition factor (CF) was not significantly different between the sexes among all fish during different months (p>0.05). The present study represents the first comprehensive information on the population structure of A. mento in the Seyhan Reservoir. The results of this study will contribute to the population management and conservation of this species and be useful in increasing knowledge on its ecology and biology.

Probiotics can improve growth, survival and resistance to pathogenic organisms of the cultivated species in aquaculture systems with water recirculation. However, their possible benefits on biofloc systems have been less studied. In this study, the benefits of Bacillus amyloliquefaciens bacterium, on a biofloc culture of Litopenaeus vannamei were evaluated. B. amyloliquefaciens was applied as dissolved in water. To our knowledge, no previous assays on biofloc systems have been published, and on recirculation systems it has only been tested mixed with feed. The objective of the present study was to evaluate the effect of B. amyloliquefaciens on water quality, growth parameters and the immune system of shrimp. Three concentrations of probiotic were tested in triplicate (9.48 × 104, 1.90 × 105, and 3.79 × 105 cfu ml-1) and were compared with the control (without probiotics). Water quality parameters such as nutrients and suspended solids were monitored. In L. vannamei, growth, survival and their immune system parameters (total protein concentration, cell number with apoptosis and percentage of granular and hyaline hemocytes) were studied. The results showed that the application of B. amyloliquefaciens did not produce significant differences in water quality or shrimp growth. However, it showed significant improvements in the immune system. As compared with the control treatment, an increase in the total protein concentration and granular hemocytes, and a decrease in the cell number with apoptosis in the hempolymph were observed. Thus, we can conclude that B. amyloliquefaciens provides greater resistance to shrimp against the attack of pathogens in biofloc systems.